Armoring and stressing rod for concrete

ABSTRACT

ARMORING THE STRESSING ROD FOR REINFORCED AND PRESTRESSED CONCRETE WHICH HAS AN INTERRUPED HELICAL THREAD CONFIGUARTION WITH THREAD SEGMENTS EXTENDING ON OPPOSITE SIDES OF THE ROD SURFACE TO FULL HEIGHT ONLY OVER ONE-THIRD OF THE ROD CIRCUMFERENCE AND WITH THEIR ENDS MERGING WITH THE SURFACE OF THE ROD.

Feb. 9, 1971 u. FINSTERWALDER ETAL 3,561,185 ARMORING AND STRESSING ROD FOR CONCRETE Filed Sept. 6, 1968 INVENTOR Ulrich Finsterw Georg Kern BY Ernst Bock United States Patent Ofice 3,561,185 Patented Feb. 9, 1971 3,561,185 ARMORING AND STRESSING ROD FOR CONCRETE Ulrich Finsterwalder and Georg Kern, Munich, and Ernst Bock, Peine, Germany, assignors to Dyckerhotf & Widmann Kommanditgesellschaft, Munich, Germany, a firm Filed Sept. 6, 1968, Ser. No. 757,851 Claims priority, applicltatign (ermany, Feb. 12, 1968,

U.S. Cl. 52-737 7 Claims ABSTRACT OF THE DISCLOSURE Armoring the stressing rod for reinforced and prestressed concrete which has an interrupted helical thread configuration with thread segments extending on opposite sides of the rod surface to full height only over one-third of the rod circumference and with their ends merging with the surface of the rod.

BACKGROUND OF THE INVENTION The invention relates to armoring and prestressing means for concrete. More in particular, the invention is concerned with an armoring and stressing rod for concrete having hot rolled, helically formed ribs which are adapted to form parts of a thread. These elements are more colloquially defined in the industry as bars.

A concrete armoring rod or bar is known from applicants U.S. Pat. No. 3,119,203 which has hot rolled, helically extending ribs that form parts of a thread which threadedly receives an anchoring member provided with a corresponding inner thread. By means of this invention an entirely new type of armoring rods was created with which, in order to provide a possibility for threadedly mounting connecting and/or anchoring members it is no longer necessary to perform chip removing operations such as cutting in or operations for the chipless deforming such as rolling on a thread at the ends of the rod. It had been discovered that it is possible in the production of the steel rod by the hot rolling method to roll on ribs, which if they are located along a helical line and extend only over a part of the circumference are sutficient to transmit the forces of the rod into the anchoring or connecting means. However, the rolling technique used for the known application of the ribs along only one side of the rod introduces certain disadvantages due to the one-sided introduction of the forces. A further shortcoming of this armoring rod is that, due to one smooth or unobstructed side of the rod it cannot be employed for the normal steel reinforced concrete construction because it does not meet the requirements for this type of construction.

In order to make possible the use of a steel rod having hot rolled helically extending ribs in normal steel reinforced concrete construction the concrete armoring rod disclosed in US. Pat. No. 3,292,337 was created, where the side of the rod opposite that which presents the thread ribs is provided with hot rolled depressions. Between these depressions there remain lands or ribs which are disposed in such a manner, that their outer confines are located on the other side of the rod at the continuation of the cylindrical plane forming the core of the rod. As far as profile and spacing of ribs are concerned, they are formed according to the principles of deformed concrete reinforcing bars. The position of these ribs is so arranged relative to the thread ribs at the opposite side of the rod that a threadedly mounted connecting and anchoring element will rest against the outer limits of the ribs.

There was created an armoring rod that can be utilized as stressing or tensioning rod, in which the applied stressing force's are absorbed by anchoring elements threaded onto the helically extending ribs on the one side of the rod as well as armoring rod in conventionally reinforced concrete construction, because for this purpose ribs were available on both sides of the rod that are independent of each other. Notwithstanding the production that is complicated in this case, because the surfaces to be rolled on the opposite sides of the rod are at different distances from the rod center and accordingly demand different surface speeds for the thread producing rollers, also this rod did not solve the problem which was presented by the one-sided introduction or application of forces by the thread ribs.

SUMMARY OF THE INVENTION Applicant has now discovered that the armoring rods for concrete particularly stressing or tensioning rods can be further improved by providing a rod where the helically extending ribs are disposed on opposite sides of the circumference of the rod where the ribs extend to full height only over approximately one-third of the circumference of the rod and the end surfaces of the ribs merge with the surface of the rod.

The end surfaces of the ribs are suitably inclined toward one another. They may be curved or planar and the ribs may be arranged to define a double thread.

With respect to profile and distance the ribs may suitably be formed in accordance with the principles of deformed concrete reinforcing bars.

By constructing the concrete armoring rods in accordance with the invention as rods having ribs disposed along a'helical line on both sides of the rod, all shortcomings of known armoring rods are avoided. The use of such rods in producing prestressed concrete causes the tension forces to be imparted to the anchoring and connecting members from both sides, so that the load on them is distributed more evenly than is the case with rods of the prior art. It has now been found that rods of this new type can be produced in a much simpler fashion than rods with different configurations on opposite sides of the rod because with armoring rods in accordance with the invention the distance of corresponding areas of the rod surface or rib surfaces from the center of the rod is always equal and thus the upper roller and the lower roller operate at the same circumferential speed. In addition, if the ribs which are primarily intended to serve for imparting and for anchoring the forces of the rod, are formed to meet the requirements for deformed concrete reinforcing bars, this armoring rod can also be utilized in the same advantageous manner in reinforced concrete construction.

BRIEF DESCRIPTION OF THE DRAWINGS Further useful features of the invention will become apparent from the following description of an embodiment of the armoring rod illustrated in the accompanying drawings, in which FIG. 1 is a cross-section of the armoring rod in accordance with the invention taken along lines H-H in FIG. 2 or 3,

FIG. 2 is a side view of the rod with ribs along the lines of a single interrupted thread, partly in section, and

FIG. 3 is a side view of a rod similar to FIG. 2 with ribs along the lines of a double interrupted thread and having a steeper pitch.

The armoring 1 is provided with ribs 2 on two oppositely disposed sides which ribs are produced during the rolling of the rod by suitably calibrated rollers. These ribs extend to full height only over about one-third of the circumference of the rod. They fade down to zero toward the plane of symmetry 8-5 which passes through the center 3 of the rod and their end surfaces 4 are inclined toward this plane of symmetry. Thus there remain unobstructed surface areas between the ends of the ribs which are displaced by angles of substantially 180 relative to one another.

The arrangement of the ribs provided in accordance with the invention that encompasses a total of about twothirds of the circumference of the rod, while between them one-sixth, i.e., one-third is free of ribs, permits optimum utilization of the material in connection with the possibilities afforded by the roller technique, and this for the material of the rod as well as also for the material of the anchoring nut to be threadedly mounted thereon which is generally of lower quality than that of the rod.

In addition to this advantage it should also be noted that, while the ribs on one side of the rod in accordance with Pat. No. 3,119,203 are additional means for anchoring the imparted tensioning forces, these forces cannot be added to the active or supporting cross section of the rod. However, a rod provided with ribs on both sides affords the added advantage that in any cross section taken transversely of the axis of the rod at least one rib is included, so that the cross sections of the ribs reinforce the supporting cross section at least partly. This reinforcement may amount to as much as up to 50% of the cross section of the ribs.

Normally the thread is a single thread in which the pitch corresponds to the space between two ribs and one rotation of the anchoring body advances the same by that space. However, the pitch of the thread can be steeper, for example it may be a double thread, so that one rotation advances the anchoring body by two of said spaces. Thus the cross section of the rod is exploited to greater advantage.

Where the ribs are along the lines of a double interrupted thread as illustrated in FIG. 3, the pitch is steeper as with a single interrupted thread; however, the pitch must be such that the ribs still offer sufficient frictional resistance to prevent nuts or threaded sockets or sleeves from slipping, i.e., there must be automatic braking. From this we derive for tensioning steel rods of a diameter of 26 mm. for example with a friction factor of ,u=0.3 a thread distance of 13 mm.

The double thread affords several advantages which were proved by tests: Full participation of the weight of the ribs in the supporting cross section, and improvement of the dynamic carrying capacity. Easier turning facility of the threaded parts due to greater pitch. Furthermore, due to the double threads the steel engages transversely not only at one point but at two points of the tubular wall of a sleeve or nut, which provides for better frictional conditions.

Having now described my invention with reference to the embodiment illustrated in the drawings, we do not wish to be limited thereto, but what we desire to protect 4 by Lettters Patent of the United States is set forth in the appended claims.

We claim:

1. Ribbed bar, particularly tensioning bar, having rolled, helically extending ribs defining parts of a thread configuration along the path of an interrupted double thread, said ribs being provided on two oppositely disposed sides of the circumference of the bar and extending to full height only along one-third of the circumference of the bar, said ribs having end surfaces merging with the surface of the bar and the areas of the bar intermediate proximate ends of said ribs being unobstructed surface areas.

2. Concrete armoring rod, particularly tensioning rod having hot rolled, helically extending ribs defining parts of a thread configuration, said ribs being of the same configuration and provided on two oppositely disposed sides of the circumference of the rod, said ribs extending to full height only along one-third of the circumference of the rod, said ribs having end surfaces merging with the surface of the rod and the areas intermediate the ends of said ribs being unobstructed surface areas of said rod.

3. Concrete armoring rod in accordance with claim 2 where said end surfaces of said ribs are inclined relative to one another.

4. Concrete armoring rod in accordance with claim 2, where said end surfaces of said ribs are flat planar surfaces.

5. Concrete armoring rod in accordance with claim 1, where said ribs are disposed along a path of double thread in the manner of an interrupted double thread.

6. Concrete armoring rod in accordance with claim 5, where said end surfaces of said ribs are inclined relative to one another.

7. Concrete armoring rod in accordance with claim 5, where said end surfaces of said ribs are fiat planar surfaces.

References Cited UNITED STATES PATENTS 1,151,947 8/1915 Havemeyer 52-74O 3,119,203 1/ 1964 Finsterwalder 52 223 3,292,337 12/1966 Finsterwalder 52738 OTHER REFERENCES Menzel, Carl A.: A Proposed Standard Deformed Bar for Reinforcing Concrete, Portland Cement Association, Chicago, Ill., 1942, pp. 44-49.

FRANK L. ABBOTT, Primary Examiner J. L. RIDGlLL, JR., Assistant Examiner US. Cl. X.R. 52740 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,561 .185 Dated February 9, 1971 Inventor(s) Ulrich Finsterwalder, Georg Kern and Ernst Book It is certified that efror appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 50, numeral "1" at the end of the line should be --2-.

Signed and sealed this 1 at day of June 1971 (SEAL) Attest:

EDWARD M.FLE'IGHER,JR. WILLIAM E. SGHUYLER, Atteating Officer Commissioner of Paten l FORM PO-105O (10-69) I 'uscoMM-oc so 

